Apart from these programmable registers , some other registers are also available which are not accessible to the programmer . These registers include -

• Instruction Register(IR).


• Memory address and data buffers(MAR & MDR).


• MAR: Memory Address Register.


• MDR: Memory Data Register.


• Temporary register for ALU use.

ALU of 8085 :

The 8-bit parallel ALU of 8085 is capable of performing the following operations –

Arithmetic : Addition, Subtraction, Increment, Decrement, Compare.

Logical : AND, OR, EXOR, NOT, SHIFT / ROTATE, CLEAR.